Sudoku Institute Puzzle Book (book)

Plot Summary:

Take a look at this new approach to the puzzle craze that's sweeping the nation. Returning the game to its Japanese roots, this book features the aims of sudoku: - to broaden minds and increase mental sharpness - together with a martial arts belt system of grading the puzzles in order of difficulty from yellow through all the colours to black and red. The puzzles range from the simple 6 x 6 squares via increasingly difficult 9 x 9 grids to a series of mind-bending 16 x 16 grids. And, for those talented and brave enough, there is a 25 x 25 Red Belt Challenge! [1]